How to test ECMAScript modules in the browser

To run our test file in the browser we need to make a couple of adjustments. Instead of Node's assert we use chai. Also, there is no need to load node-fetch since fetch is built into the browser.

import Tom from 'test-object-model'
import 'https://www.chaijs.com/chai.js'

const assert = chai.assert
const tom = new Tom()

tom.test('Math.random() should return a number between 0 and 1', function () {
  const result = Math.random()
  assert.equal(typeof result, 'number')
  assert.ok(result >= 0 && result <= 1)
})

tom.test('REST API should return the current todo item', async function () {
  const response = await fetch('https://jsonplaceholder.typicode.com/todos/1')
  const todo = await response.json()
  assert.equal(todo.userId, 1)
  assert.equal(todo.title, 'delectus aut autem')
})

export default tom

Run the tests in Chromium using web-runner.

$ web-runner browser.mjs

Start: 2 tests loaded

✓ browser Math.random() should return a number between 0 and 1 3.7ms
✓ browser REST API should return the current todo item 122.0ms

Completed in 134ms. Pass: 2, fail: 0, skip: 0.